1. Field of the Invention
This invention relates to a measuring technology of the tip temperature of a soldering iron, and more particularly to a soldering iron temperature regulator capable of calibrating the measuring error of a temperature sensor at ordinary temperature.
2. Description of the Prior Art
The assembling work of various electric appliances using electronic parts such as ICs requires a job of soldering semiconductor devices which are not resistant to heat. In soldering job, therefore, it is important to be careful so that the tip temperature of the soldering iron may not exceed the specified temperature, in particular.
Recently various soldering irons capable of controlling the tip temperature constant have been developed (e.g. the Japanese Laid-open Patent Sho. No. 61-37368).
In this type of soldering iron, generally, the heater is heated according to a preset temperature, and the iron tip is heated accordingly, and the temperature of this heated iron tip is detected by a temperature sensor, and this detected temperature is compared with the preset temperature, and as a result of this comparison, the temperature is controlled depending on the difference of the both temperatures, so that the tip temperature may be kept always at the preset temperature.
Meanwhile, in this type of soldering iron, it is necessary to calibrate the intrinsic measuring error of the temperature sensor when replacing the temperature sensor or at the time of shipping inspection.
Conventionally, this calibration of intrinsic measuring error of temperature sensor was conducted on all soldering irons in the following procedure.
That is, on all soldering irons, the heater of the iron tip is energized to heat the tip to an operating temperature, and the tip temperature is measured by the temperature sensor. As a result, if the temperature measured by the temperature sensor does not coincide with the preset temperature, the measuring error of the temperature sensor is calibrated.
In such method, however, since it takes much time for heating by the iron tip heater, a long time is required for calibration of the measuring error of temperature sensor, and the job efficiency is very poor.
Besides, in this calibration job, the iron tip is darkened due to the heating of the tip by energization of the heater, and the product value as the soldering iron is lowered. In fact, due to this discoloration, the users often misunderstand that second-hand pieces are mixed in the products, not knowing such procedure, and the manufacturers have to settle the claims.